MK 47 Mutant Torture Test

We’ve posted a couple of times about the interesting CMMG MK 47 Mutant, which mates an AR-style operating mechanism to an intermediate-length upper receiver and a lower receiver that takes AK magazines. The marriage of the AR-15’s direct impingement operating mechanism and the 7.62×39 round is an interesting one, and many may be curious how those two perform together in an extended firing session (such as a carbine course). Mrgunsngear has obliged us with an (attempted) 1,000 round-count firing session with the Mutant.

Unfortunately, near the 600 round mark (600 rounds in that session; it had previously had about 1,200 rounds through it) the rifle began having issues. Initially, my suspicion was the ammunition: The rifle was failing to extract, which is normally an ammunition issue, but that hypothesis was disproven as the rifle continued to fail to operate properly:

What was the issue? Mrgunsngear goes into detail below:

The rifle did not suffer from its ammunition (though it did not agree with every magazine tried, and Mrgunsngear was very thorough in trying a wide variety of mags), or its direct impingement mechanism, but the screw-retained gas block came loose and failed, causing the malfunctions. This problem shouldn’t concern most users of the rifle, but does highlight the importance of pinned gas blocks (or at least staked screws) on rifles that will see hard use.

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • Michael

    Thanks for the warning. (Pulls out BFH and staking punch)

  • Andrew Hobby

    I’m still on the fence about this rifle. Why not just buy an AK? Or, for the cost of this rifle, buy an AK and an AR?

    • Xanderbach

      I have both AKs and ARs, and prefer the ergonomics of the AR, yet an AK is my go-to rifle since it’s basically guaranteed to work. Probably your best bet for both is the new Galil ACE, since it’s an AK with improved ergos. Same price as the MK47, but better charging handle and that rock-solid AK action.

      • stephen

        Its strange when I hear people say stuff like ‘my ak is my go-to rifle since its basically guaranteed to work’. I guess there are a lot of crappy AR builders?

        I spent a career in army with 12 years overseas using numerous ARs and never had any problems save one that had some broken trigger pins. Heck the 2 ARs I have now (stag arms model 2 and ruger sr556) haven’t given me any problems with the 12K rounds I have put thru them (so far).

        I guess I got lucky?

        • Xanderbach

          Could be. I spent a tour in the army myself, and have nothing but dislike for the reliability of the M16/M4. Could be because my M4 crapped its pants in the sandbox (armorer had no idea why it was double feeding. most likely under gassed or bad mags) so I ended up using a yugo AK for 4 months while waiting for replacement parts/weapons. While this may not be a fault of the design, that worn out AK always worked, regardless of conditions outside. I could also stick it just about anywhere without fear of harming it. In Salt Lake in ’02 (winter olympics) while on guard duty, one of our guys smacked his buttstock (M16A2) too firmly on the ground, and it shattered like glass. Then again, it was -19 F outside, but still. Just because your weapons were great doesn’t mean they all are, and just because you like something doesn’t mean everyone else does. I live in a desert now- AZ. Environment is very close to Iraq here, what with all this sand and grit in the air. So if bad things happen, I pass over my ARs and grab my Maadi AK.

          • Yeah, the AK is always more forgiving. But the most recent improvements to the M4 have really upped reliability. Also a good piston AR like the Sig 516 or Adams Arms will go bang every time. IMO.

  • MPWS

    As has become usual, this is just another tinker-toy. When I rear this: “The rifle was failing to extract, which is normally an ammunition issue ” I say to myself: What on Earth they are doing?
    The very essence and reason for radical taper of M43 round was to enhance extraction at any possible circumstance. If someone did not grasp this, they have no clue what AK is about and should stop mimicking it.

    • J

      do you not understand what happened?
      the gas block came loose, leading to a loss in gas pressure.

      • Vitsaus

        So the real innovation is introducing AR problems, to the AK platform? Game changer.

        • That’s a screwed-on gas block problem, not an AR problem.

      • stephen

        Yes the ‘torture’ of 600 rounds was just too much for the gun.


  • stephen

    Since when is 1,000 rounds considered ‘torture’?

    • Vitsaus

      Since the majority of kids with the most tactical of “accessories” mainly use their guns for taking pictures to post online.

      • stephen

        Thanks for keeping me current in the world of ‘tacticool’. Its so different than what I experienced in the infantry. There should be a disclaimer stating as such in the video.


    • Dan

      Oh they mean torture on a persons wallet.

    • Agreed. To an AK or SKS, 1,000 rounds is nothing. Also to ARs, Mini-14s…

  • wolfgar

    I remember when the 5.56 Chinese AK’s were imported to the US and had reliability problems which turned out to be a gas port that was drilled too small. Any time you change calibers with any proven system problems can arise. The AK is not as reliable with the 5.56 as with the standard Russian calibers which were desighned with more case taper. The AR DI platform is the opposite. In any event this video did prove the superiority of a pinned gas block.

  • Timothy Wahl

    anyone that believes an ak will run 100% of the time hasn’t spent much time shooting…

  • noguncontrol

    time to test this against an ar in .300 blk!!! the battle of the .30 caliber intermediate rounds!!!